I got an email a couple of nights ago from a retired engineer named Carl Litzkow. Carl does not consider himself a pulsejet designer (yet!) but has well-honed skills and a well-equipped metal shop and wants to build things that I design. However, he didn't want to slavishly copy something, so he said he had fabricated an FWE style chamber tapering from 3.5 to 1.75 inches in a mere 31-inch length and an unusual spark plug location! It features a nice partial hemisphere front dome, as well. He wondered if I would recommend a straight pipe to make about a 7.5-foot engine. Instead, I threw his chamber quickly into UFLOW1D and came up with the Thin Lady, as you see below.

I tried to make this engine even shorter, but couldn't get the kind of resonance I expected, so this is what I ended up with. As you can see in this one, I sacrificed some exhaust velocity for higher massflow. The narrow straight tube cross-section is 57 percent greater than my usual 1.25-inch tube, so this will be a stronger engine in any case, but the long skirt should make it even better. We'll see.

Carl has agreed to build it as I drew it and test it out. I still haven't shown a fuel pipe on the drawing, but it will probably just be a straight stinger of 1/4-inch brake line, feeding propane vapor.

The first UFLOW graphic shows the resonance of the pipe as a whole, using Graham's low-pressure method; the second shows one cycle of expansion and breathing via the initial high-pressure method. This ought to be a fine-running beast, I think.

I haven't found out from Carl yet whether he will be able to get a series of construction photos; I certainly hope so. It would be fun to see what his shop setup is like, too. And, I'm encouraging him to at least put up a post here to introduce himself.

Larry Cottrill wrote:I got an email a couple of nights ago from a retired engineer named Carl Litzkow. Carl does not consider himself a pulsejet designer (yet!) but has well-honed skills and a well-equipped metal shop and wants to build things that I design.

Larry--I envy you!!

I've had several collaborations, since I started my PJ "career"; these have had mixed results--and I'm on my own, with the current effort(s).

There's so much to do, IMHO; I wish I had a partner who could share the current load. I need a technically proficient person, with some time and $$ to expend on the effort.

Time will tell.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

Why is that spark plug location so unusual? I usually go with the front or side of the engine so the starting wires dont get melted by comming into contact with the engine. The most unusual spark plug location I have tried is entirely outside the engine, or perhaps that engine that shot it up into the air...

If he has some good tube spinning equipment I have some designs he might also be interested in making. Basically a super escopette.

LoL Bill dont we all. Think of how many 10,000's of man hours it would take just to develop 1/4 of Larrys designs. Has anyone even counted how many "proposed engines" he came up with? Do we even have a number system capable of expressing such a thing :P

Eric

Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

Eric nice drawing, but beware for those people with callipers.
Because I think the drawing is not in real perspective.
You can see it on the strait sections the have to look smaller in the distance, just as looking over railroad, in the distance the rails seems to disappear in one line.

Whatâ€™s the purpose of the bulge?, maybe tuning the pressure waves with the sound waves?.

Hmm, since Eric is obviously on to the idea, I might as well stop sitting on it.

An engine like this, properly designed, will act like an inline blast compression engine. The deflagration in the primary CC will drive gas into the 2ndary CC. The flame-front will generate a supersonic conical flame-front that slams into the unburned fuel/air that slows down and gets compressed at the back end of the 2ndary CC - causing a large portion of the charge to undergo near constant volume combustion.

There is some literature out there that describes a Pulse Detonation engine that uses a similar technique.

Ah yes, is it an isometric view, or do the various parts expand outward at just the right rate to make it appear to be an isometric view by negating the vanishing point effect :P. That part doesnt matter at all because it was just a sketch with no regards to dimensions or proportions so just copying wouldnt work very well at all.

The main idea was to better control wave propogation and timing, the secondary combustion chamber and the blast compression effect would be a manefestation of that.

Eric

Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

I'll try, with the two files below. Re-name, eliminating the .TXT suffix, leaving the .IMM intact for UFLOW. I've also shown the two Pipe pages - the only difference is the initial pressure column. I also show the Data page for the high-pressure run - the only thing changed for the low-pressure (suction) run is changing the run duration to 0.1 second. Finally, how the Contour page should look if the Pipe data is dimensionally correct.

Are you taking advantage of the initial velocity column at all?

No - have never used it.

CORRECTION: Note that in my original post, I thought I was out in the intake flare with the last Data Point (white line) - it is actually a little way down into the intake pipe.

I am really really amazed with all your UFlowing you havent played with the initial velocity tab.

Basically if you have initial velocity of 0 you are only testing the first pulse of the engine.

If you do the initial cycle of v= 0 m/s, and check the results, look and see what the gas velocities are at the various points in the engine at the time where ignition would occur durring the next cycle. Take those values and put them into the initial velocity column and do another test, which would effectively simulate the start of the 2nd cycle.

Repeat that until the engine stablizes, there will be less and less gain each time, and you should then have what is happening when the engine is running, more closely at least.

If you dont play with the velocity you are basically just looking at how well the engine pops and bangs, and the kadency afterwards, not a running engine.

Some engines reach peak thrust very quickly, others may take 4 or 5 times as many cycles. Its the same principle as Forrests describes in his limit cycle behavior post. The same thing can be seen (and heard) with throttling the engine if you dont have any "lag" in the fuel system.

Maybe we could all petition the guy who made Uflow to create a pulsejet version which will add a pressure pulse to each cycle.

Eric

Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases